1. Field of the Invention
The present invention relates to a novel soybean hydrolyzate and a process for preparing the same.
The hydrolyzate is a high nutritional value and excellent in protein absorbability. Moreover, it is free from bean-like or grass-like smelling that is characteristic of soybean. It is also free from bitter taste. Consequently, it is valuable food as protein source.
2. Description of Prior Arts
Soybean is a food material rich in proteins, fats and undigestable carbohydrates of good quality, which is highly useful as nutritional supply. The soybean food desirably makes use of entire constituents of soybean grains. For the use of the whole grains of soybean are known two processing methods, a dry process (Japanese Patent Publication No. 48-19946) and a wet process (Japanese Patent Laid Open No. 50-4263). According to the dry process, soybean grains are compressed to such an extent that they are not de-fatted, dried and coarsely divided to remove the seed coat; the remaining seed lobes of the soybean are steam-cooked in a steam cooker while deodorizing odor from the fats and dehydrating water attached to or impregnated in the seed lobes in a short period of time by means of vacuum suction; and then the steam-cooked product is pulverized successively to a medium particle size and to a fine particle size to produce deodorized fine particles of soybean. The heat treatment in the dry process removes unpleasant bean-like and grass-like odors, and further inactivates trypsin inhibitors and nutrition-inhibitory substances such as hemaglutinin contained in the soybean. However, the heat treatment is disadvantageous in that solubility of the protein is much reduced, and its absorbability becomes lower.
According to the wet process, on the other hand, raw seed lobes of soybean are heated so as to soften them and inactivate lipoxydase enzymes, followed by formation of a slurry of the soybean and water, and the slurry is homogenized in a high-pressure homogenizer to produce a soybean drink. Although the wet process allows use of entire constituents of the soybean, the pressure homogenization to a fine homogenate does not produce sufficiently soluble proteins.
In this respect, combination of a treatment with enzymes or microorganisms has been considered in the wet process. However, the use of a protease is associated with formation of peptides with bitter taste, thereby making oral ingestion difficult. In the use of a microorganism there occurs the denaturation characteristic of fermentation. It also requires a considerably long period of reaction time.